Why are most roads and parking spaces in England narrower than in the rest of Europe?

Single track country roads are common, but rarely required except for the last little bit of the journey. Unfortunately some route planners seen to like to shave a couple of minutes of the trip time by using miles of them. I've come across a good few in France too. Widening would be very expensive (land purchase as well as construction) and being so old they tend to be too bendy to be fast anyway.

In urban areas, the roads and the houses they serve aren't so much narrow as used to store too many cars - when much of our housing stock was built, car ownership for normal people wasn't a thing.

The network of main roads should get you very close to your destination, so you only have to use such narrow roads for the last few miles (with exceptions for some very rural areas, but they're still not needed as through routes). Motorways (blue signs, numbered Mx or Ax(M)) are high capacity, with wide lanes and are intended to be the first choice for long distance (e.g. the M4 from London takes you to near Bath). There are dual carriageway A roads (overlapping eith designated "trunk" roads) to a slightly lower standard. Then you have single carriageway A roads, like the A46 that links Bath with the M4. Another quick road despite the cotswold hills. These can also be classed as trunk roads. Most villages can be reached by B roads which are often wide enough for a lane in each direction, but not always.

Given all that, country lanes don't need to be fast roads. In fact in some places where a road is just wide enough for a central white line, it's omitted to encourage slower, more cautious driving.

As for parking spaces, it's largely a matter of old standards being based on the typical cars of decades ago, which were far smaller than much of what you see now. There's little incentive to repaint bigger spaces to modern standards as you can get more cars into smaller spaces - more profit if you're charging for parking. Even if parking is free as at a supermarket, repainting costs money and reduces capacity for customers. I drive a Transit campervan, and for width it's OK in a typical supermarket space (being careful as I open the door). That struggles with length, but the solution is normally to park at the furthest edge of the car park, where I can overhang the back of the space, and if I o stick out, I'm not massively in people's way. That also generally means I can have a free space on at least one side.

A combination of historical factors and legal/practical ones.

One is simply that England was the first country to undergo the industrial revolution. Considerable urban sprawl developed long before the idea of the motor car even existed, and yet more before the idea that a regular person could afford one did. And unlike in much of mainland europe, very little of this was ever razed by war. So there's a lot of narrow urban streets (with little parking, and parked cars tend to cause crowding) even in "non-historical" areas. Continential europe provides far more super-narrow streets, but they're usually restricted to small medieval central areas.

Another factor is that England is very densely populated, so land is expensive. On the European mainland, only the Benelux countries are comparably dense. Although similar narrow roads are also prevalent in Scotland and Wales, so that perhaps isn't a major factor.

Also relevant is the nature of land ownership in the UK. Almost all land is privately owned - public land is very rare, and any "common" or "unowned" land can be seized by a private person or company that wishes to do so. Land rights are also fairly strong. This makes it legally difficult as well as expensive in terms of construction, to widen all the country lanes that exist on the route of some historical cart track. This combined with the fact that British governments dislike investing in infrastructure (or any kind of investment) compared to a "typical" European government.

I can't say I've ever noticed any differnce in size between European major routes and parking spaces and English ones.

With regards to parking spaces, here the extremely rapid inflation in car sizes over the past 15 years is relevant. The "typical" car has grown very rapidly, having only grown slowly for the 40 or so years before that. And places are reluctant to reduce the number of spaces available by making parking spaces bigger.

They aren't. Roads and parking spaces are about the same size in the UK and in continental Europe. UK car spaces might even be on the large side.

Let's compare some modern standards for a dual carriageway with two lanes in each direction:

• UK (source): 7.3m in each direction.
• Ireland (via Wikipedia): 7m in each direction.
• France (source): 3.5m per lane, so 7m in each direction.

Minimums for a rural road with two-way traffic:

• UK (source): 5.5m.
• France (source): normally 7m (2×3.5m) for new roads, but many rural roads can be down to 5m.

Minimums in cities for a street:

• UK (source): the minimum street width is normally 5.5m for two-way traffic, but can occasionally get down to 4.8m. Minimum 6m for a bus route.
• France (source): 3.25m or even 3m per lane.

Sizes of a parking space:

• UK (source): minimum 2.4m×4.8m for a parking bay. Minimum width 1.8m for an on-street parking lane.
• France (source): minimum 2.3m×5m for a parking bay. Minimum 1.8m for an on-street parking lane mentined in Wikipedia).

Conclusion: if there is any difference, it would be because the UK has more older roads that don't conform to modern standards, not because UK roads of comparable type and vintage are narrower. I don't have numbers for that, but I doubt that it is the case if you actually compare like for like — low-traffic country roads, modern highways, historic city centers, modern urban developments...

country roads were ridiculous to navigate, with one single extremely narrow lane for each direction making each pass of a oncoming vehicle a near accident experience.

This is my experience of country roads in France. The fields on either side of the road existed long before automobiles, and wider roads weren't needed back then. Same as in the UK.

Even more ridiculous were the narrow parking lots and parking garage ramps. Two cars can park perfectly beside each other but none of them will be able to open their doors conveniently

This is my experience of parking garages in Paris. The city was largely built before cars, so parking has to be crammed in very little space. Same as any UK town that was built before cars.

Europe tends to waste significantly less space on cars than most of the US, but the UK is not different from the rest of Europe.