The passage in Isa 40:9-31 is a wonderful eulogy about the greatness of God. It uses a series of similes to show how great God is:
- V12 - measures all the waters (= seas) in the hollow if His hand
- V12 - measures the heavens with the span of His hand
- V12 - hold all the dust of earth in a basket
- V12 - can weigh all the mountains in a scale
- V13 - greater than all wisdom - no one can teach Him anything
- V15 - all the nations are but a drop in the bucket to Him
- V15 - the nations are but a speck of dust on God's scales
- V15 - the islands are like fine dust to Him
- V16 - all Lebanon's wood would not be enough for God's needs
- V16 - all the animals in the world would not be enough for God's sacrifice needs
- V17 - all the nations are as nothing to Him
... and so forth. Thus, "the nations are like a drop in a bucket" is absolutely consistent with the extended hyperbole in this passage - God is truly great and awesome (Deut 10:17, Ps 68:35, 89:7, Dan 9:4, Neh 1:5, etc). There is none like Him.
Matthew Henry observes for this passage:
40:12-17 All created beings shrink to nothing in comparison with the
Creator. When the Lord, by his Spirit, made the world, none directed
his Spirit, or gave advice what to do, or how to do it. The nations,
in comparison of him, are as a drop which remains in the bucket,
compared with the vast ocean; or as the small dust in the balance,
which does not turn it, compared with all the earth.