(Just in case i was misunderstood earlier, the task of the central bank would be to offer static interests loans rather than devaluating existing ones. While this likely will contribute to some inflation I do not see it as a signifanct devaluation as explained below.)

I disagree with the direction of the threat here. While I do agree that state financing through money printing (and I'm never able to remeber the english word for it...) would devaluate the USD if kept up for a significant period of time and or volume, do remember, that the primary threat of inducing bankruptcy comes from inflating interests spiraling out of control as a consequence of uncertainty and often speculation against the country reinforcing each other. However, if the central bank offers a credible vehicle that guarantees the states ability to finance itself at a reasonable rate both do not exist. If done well in the best case the financing vehicle may therefore never need to be used - as the open market rates would still be raised, but not exceed acceptable limits either. Worst case, you do need your vehicle somewhat. This would increase the supply of USD slightly, thus reducing its exchange rate slightly. This would then require a slight increase in interests to keep your investors but that should be entirely manageable.

The other threat here would be hyperinflation that could ensue if the state financing is left without a limit though this is hard to imagine, given the position of the United States in the worlds trading order, and requires active political botchering which we will not assume here.