Is any distribution from a foreign estate taxable in the U.S.? My mother in law passed and she is Canadian, as my wife. Since tax was paid in Canada, would I owe here?

What was distributed ?     Cash inheritances are not taxable income. 

we don't know what the distributions represented.  if it corpus/principal of the trust it's not taxable. if it's income it's taxable.  we also would need to know the year-end of the trust if it's income.   a fiscal year-end of the trust could mean any income distribution would not be taxable until the 2021 tax year.  most likely the trustee would supply you with info especially if there's an income distribution that is taxable in Canada.  hopefully, someone with more knowledge of Canadian trusts will respond