Congress takes its power-of-the-purse role&nbsp;seriously, which is why a president's budget almost always lands on the other side of Pennsylvania Avenue with a bit of a thud.President Trump's blueprint&nbsp;for the next fiscal year,&nbsp;released Thursday, was no different.The reaction illustrated why, despite the significant attention they are drawing, Trump's proposed dramatic cuts will likely be scaled back, changed or eliminated altogether.&nbsp;The president's spending plan&nbsp;was only the first step in months of negotiations between the White House and Capitol Hill over how to allocate funding. Trump will put forward a more detailed spending proposal&nbsp;in May, and various legislative committees will scrutinize his requests, calling on Cabinet secretaries, agency heads and others in the administration&nbsp;to explain their wish lists.House Speaker Paul D. Ryan (R-Wis.) effectively took a deep breath Thursday, a reminder that the plan was merely the start of a long, legislative grind that will play out for months, until funding for the new fiscal year is needed when it begins Oct. 1."When the president&nbsp;submits a budget, that is a beginning of the budget process," said Ryan, a former House Budget Committee chairman whose own past proposals, particularly his steep cuts to revamp Medicare, were&nbsp;nowhere to be found in Trump's initial plan."Do I think we can cut spending and get waste out of government? Absolutely," Ryan said. "Where and how, and what numbers, that&rsquo;s something we&rsquo;ll be figuring out as time goes on."The Oct. 1 deadline is particularly important this year because spending levels from a past budget accord are set to expire. Without a new deal, automatic cuts would take effect that many in Congress want to avoid.Trump's budget lays down a marker in that fight, and&nbsp;House Minority Leader Nancy Pelosi (D-San Francisco) had a blunt response:&nbsp;"As we have said over and over again in this room, the budget &mdash; the federal budget &mdash; should be a statement of our national values.... This budget is not a statement of values of anyone."More immediately, though, Congress will need to pass a measure to keep the government running past April 28, a self-imposed deadline when funding for the current fiscal year runs out.That is shaping up to be a more imminent showdown because Trump has requested $3 billion in supplemental funds for his promised border wall with Mexico&nbsp;and other immigration actions.Democrats are refusing to fund the border wall. Even Republicans want Trump to keep his promise to have Mexico pay for it. And that could lead to a spring funding stalemate that risks a government shutdown.Even though there might be line items to like &mdash; &nbsp;for example, many in Congress would like to beef up military spending &mdash; not as many want to make Trump's proposed cuts pay for it.11:58 a.m.: This story was updated with details on the appropriations process.