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, but you can also set up an LLC or a Limited Partnership.
If most of your investors will come from your country and few from the US, then using a Tier 1 Reg A+ might be a 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 any US State under Tier 1, you must have satisfied that State's Blue Sky regulations. Learn more about Tier 1 here.
If you will raise capital from US investors in multiple US states, then Tier 2 is the best method to use because dealing with the US states is far easier in Reg A+ Tier 2. Tier 2 offering size range is from zero to $50 mill per year.