I only see two very unlikely ways for conquering US before 1948...
a) abomb... and it would still be difficult to get them in place to break the US
b) civil war in the US.... get some of the states on your side and then "help" them against the other states...
probably there are studies about the political views of those states at that time... i didnt read any so i dont know how the tensions where in the US between those states..
a) abomb... and it would still be difficult to get them in place to break the US
b) civil war in the US.... get some of the states on your side and then "help" them against the other states...
probably there are studies about the political views of those states at that time... i didnt read any so i dont know how the tensions where in the US between those states..