Our ability to destroy universe is not dependent on existence of God.
God is beyond universe first of all.
God don’t interfere with working of universe except only when roles were created for working of universe and except when one of his beloved need him to change something.
Next thing is why can’t we destroy universe?
Answer is is immensely huge. Mind boggling huge. Extremely huge and need at least 100000 times more technology to even destroy earth then we have now.
So you want to destroy universe? Wait another hundreds or thousands years and hope society survives till then and keep developing technology to destroy universe