Am I allowed to raise capital using Reg A+ for my company that is outside the USA?
Yes. If you set up legal Headquarters for your company in the USA or Canada then you are allowed to use Reg A+ to raise capital. Most companies that take this route set up a "C" Corporation in Delaware.
If most of your investors will come from your country and few from the US, then using a Tier 1 Reg A+ can be a very good fit. The advantages of a Tier 1 are that you do not have to file an Audit with the SEC and you do not have to make revenue and profit reports each six months. The big disadvantage of Tier 1 is that when you raise money from investors in a US State, you must have satisfied that State's Blue Sky regulations. Learn more about Tier 1 here.
If you will raise capital from US investors then Tier 2 is the way to go for your offering.