They are more similar than Calvanism is to Catholicism.
From my readings, Arminianism and Catholicism have several things in common.
- Everyone can be saved instead of just the “elect”
- Grace is resistible. God can call someone to faith and repentance but a person, by an act of free will, can reject the gift of God’s grace. Faith is synergistic (us and God) instead of monergistic (comes from God alone)
- It is possible to fall from grace, that is, choose to no longer live in faith. Be it by a sinful lifestyle or rejection of a faith that they once proclaimed.
- Original sin causes mankind to be wounded (or sick) but not completely dead in our sins. This gives us the ability to be able to accept the gift of grace by faith.
All graces comes from God, Grace gives us the ability to believe and have faith. The difference is that in Arminianism all grace comes through living by faith instead of via the sacraments and good works. Living by faith can and does include sacraments and works but they aren’t means of grace. Faith is the sole vehicle of grace. Arminians strive for righteousness and perfection but trust in God and His Grace to make up the differences between their actual righteousness and the righteousness required to enter heaven. However, to stop living by faith either by falling into a sinful lifestyle or to lose faith will cause one to reject grace and lose salvation.
Contrary to popular belief, Arminianism is held by more evangelicals in the USA than Calvinism. Southern Baptist are mostly Arminian in how someone comes to faith and Calvinist only in Security of the Believer for those who have come to faith. (Although Calvinism is growing the SBC) United Methodist and almost all Pentecostal/Charismatics are Arminian. The only truly Calvinist churches that I’m aware of are Presbyterian, Reformed or Reformed Baptist. Most non-denominational churches are Arminian.