I wouldn't establish a national church, which the Founders were adamant to avoid, but I would lobby for an amendment the declares that Christianity was the preferred or official religion of the country. Modern Germany has a similar position, and it avoids all of this "all faiths are created equal" garbage. I would make it very clear that this doesn't mean that the church will be consulted on any matters of the state, but that the state would not bend over backwards to accommodate the sensibilities of other faiths in matters. This intention of this isn't to require all Americans to be Christians (which is ludicrous), but it would clearly and unequivocally state that this country is founded on Judeo-Christian principles. The Ten Commandments are welcome in the courthouse, for instance, and we wouldn't have people trying to sue high schools from offering a prayer before a football game. You're welcome to practice whatever you wish in your home or church, of course, but you can't expect the state to be willing to give equal time to Islamic/Hindu/Satanic monuments.

Other business, is that any state is welcome to leave the union at any time if that state's legislature approves secession with a 3/4 vote. The only condition is that the state must pay its per capita share of any debt the Federals have incurred. Basically, a no-fault divorce clause.

I would also include an amendment or clause that declares a base minimum 7% protective tariff for all international imports. This would kill free trade, but not be so punitive to kill international economics. Purely meant to help encourage domestic production and manufacturing.

I'd also severely neuter the power of the executive, and further concentrate power in the legislative. This includes an easier path for impeachment, and the ability for the congress to remove judges with a 3/4 vote.