Note that while St Martin is an oversea collectivity, whereas we consider Guiana to be an actual part of France not a territory or collectivity or dependance or

Note that while St Martin is an oversea collectivity, whereas we consider Guiana to be an actual part of France not a territory or collectivity or dependance or ... (the same way we did with Algeria). So France the (geo)political entity and France the country absolutely has a border with Brasil, and it is its largest land border.