re: Republicans control every branch of government and still can't repeal Obamacare

OK, you want to include lowered revenues because of the Bush tax cut (which was extended by Democrats) as part of Obama's deficit (???).

Why did Democrats not repeal the Bush tax cut when they controlled the White House, Senate and House of Representatives? You're blaming Trump for not fixing Obamacare, why not this?

Now for the numbers. Paul Krugman says "the Bush tax cuts cost $1.8 trillion" (never mind that Bush's total deficits/adding to the debt was $3.3 trillion and that $1.8 trillion over eight years is $225 billion in lost revenue per year).

For shits and giggles, we'll add "the Bush tax cuts cost $1.8 trillion" to the debt.

That leaves $5.325 trillion in "Obama debt," of which "Bush spending" was (I'm playing by your rules) $3.975 trillion (eight years of Bush war spending applied to eight years of Obama's term with no reduction -- even though there was) plus "the Bush tax cuts." (Obama's total debt was $9.3 trillion.)

That is only 43 percent of Obama's debt that you are, using your rules, attributing to Bush. That is not "most."

Edit:

And actually it's even less. The Iraq War cost $170 billion/year on average. So that's $1.36 trillion applied average to all eight years of Obama (it was lowered, so it's even less). And I forgot the $475 billion for the "Bush bank bailout." Plus the $1.8 trillion Krugman-estimated Bush tax cut "cost."

So that's $3.635 trillion in "Bush-caused deficits" applied to Obama's $9.3 trillion, leaving $5.665 trillion directly applied to Obama.

That leaves "Bush did it" at 39 percent of Obama's debt. That still isn't "most."