score:6
As Tor-Einar Jambjo notes in a comment, the Archos Elements 50d Oxygen does not support the right frequencies for 3G/4G access in the United States. Even if Free.fr has roaming partnerships with U.S. carriers, your equipment would not be able to take advantage of 3G/4G services.
According to FrequencyCheck.com, it can use the B3 (1800), B7 (2600), and B20 (800 DD) LTE bands, none of which is used in any part of the United States.
Its 3G (UMTS) radios can use 900 and 2100 MHz bands, but neither of those are used in the U.S, either.
T-Mobile is the only major GSM operator still offering GPRS/EDGE service in the U.S.; AT&T shut down its 2G network at the end of 2016, and neither Verizon nor Sprint nor U.S. Cellular ever operated a GSM/GPRS/EDGE service in the first place. T-Mobile has stated they will maintain their 2G network until 2019, but it has actually decommissioned most of its capacity, which was always more limited than AT&T's and only available at 1900MHz.