First of all "might could" is impossible. Just use one or the other.
"Then, I might go to America as well." or "Then, I might be able to go to America as well."
It's a good question about "too/as well". You can almost use them interchangeably, but apparently "as well" refers to the verb: "in the same way". "Too" refers to the noun: "and the same for me".
It's a very small difference, so don't worry too much. The idea is that someone is going to America, and you think about doing the same.