Let’s be clear, these are policy changes being made, not fiscal ones. Combined, the budgets of all three of those agencies is a rounding error, compared to the national budget. Trump wants to cut these because he is opposed to their mission and/or content, not because he genuinely thinks they are going to make any difference to the federal deficit.
The Federal Budget for 2016 was approx. $4T. CPB’s annual budget? ~$445M. That‘s about ~0.01%.